Lantibiotics are bacterially-produced antimicrobial peptides that possess unique chemical and biological properties owing to their containing a variety of unusual amino acid residues. Lantibiotics are defined as such by the presence of lanthionine or β-methyllanthionine, which are introduced by a posttranslational process in which serine or threonine is dehydrated to the corresponding dehydro residue, which then reacts in a Michael-type addition of a cysteine sulfhydryl group to the double bond of the dehydro residue to form a thioether link [reviewed in (1-6)]. Mature lantibiotics typically contain one or more dehydro residues that do not participate in lanthionine bridges. The unique properties that are conferred by these unusual residues results in their being useful components in the design of novel biomolecules (1,2,7,8).
One of the attractive features of lantibiotics is that they are comprised of gene-encoded polypeptide sequences, so their structures can be manipulated by protein engineering. Whereas this is simple in concept, putting it into practice requires the utilization of many different genetic and recombinant DNA techniques, including the removal and replacement of chromosomal segments with their genetically-engineered counterparts. Ideally, these manipulations need to be done in such a way that the engineered lantibiotic analog be efficiently produced so that useful amounts of the analog are available for experimentation, which implies a need to engineer regulatory elements. Only a few bacterial strains have been sufficiently characterized to permit these manipulations to be performed in a convenient and facile manner. One such well-characterized bacterial strain is Bacillus subtilis 168, which is second only to E. coli in the extent to which tools of genetic and protein engineering have been developed, which has contributed to the extensive use of B. subtilis 168 for the industrial production of bio-engineered materials. The advantage of B. subtilis 168 over other bacterial strains has recently been increased even more by the availability of the complete sequence of the B. subtilis 168 genome (9).